MRI

br Magnetic Resonance Imaging 1

Magnetic Resonance Imaging

An introduction to the development of MRI Magnetic Resonance Imaging 2

The Magnetic Resonance Imaging (MRI ) is a painless , noninvasive medical test through which physicians diagnose medical conditions in patients Using radio waves and magnetic fields , a complete picture of the bones tissues and internal organs is produced on a computer . It should be noted here that that the MRI doesn 't use x-rays or any ionizing radiation and the images can be printed too (RSNA , 2007 . The MR images enable physicians to

have a better evaluation of the internal parts much better than in other procedures like x-rays , ultrasound , and computed tomography etc . The working of MRI is based on the principles nuclear magnetic resonance , but is referred to as MRI instead of NMRI because of the negative association of the word `nuclear ' in the late 1970s . MRI was initially a tomographic imaging technique , which produced image from NMR signal corresponding to a slice through human body , from which it has advanced to volume imaging (Hornak , 2007

The magnetic resonance phenomenon was discovered independently by Felix Bloch and Edward Purcell in 1946 , and were both awarded the Nobel Prize in 1952 . The use of magnetic resonance for detecting anomalies in tissues and tumors was first considered in 1971 when , Raymond Damadian found that the relaxation times of tumors and tissues were different The first magnetic resonance imaging was demonstrated in 1973 by Paul Lauterbur on a small test tube sample . It was in 1975 when Richard Ernst proposed the use of Fourier Transform and phase and frequency encoding in magnetic resonance imaging . This formed the basis for the modern MRI imaging . The MRI of the whole body was then demonstrated in 1977 by Damadian (NUSM , 2002 . Several developments Magnetic Resonance Imaging 3

evolved gradually in the subsequent years in the relevant fields of echo-planar imaging and in magnetic resonance angiography . The functional MRI (fMRI ) was developed in 1993 for mapping brain function and in 1999 MagneVu developed the first portable MRI mechanism

The current MRI systems use static magnetic fields from 0 .2T to 3T . The available field strength for the open and tubular type MRI scanners has been increased by using superconducting magnets . The field strength of open magnetic systems is about 0 .7T , while fast growing MRI systems use 3T super conducting magnets . The 3T systems are however restricted to limited selection of radio frequency coils , compared to 1 .5T scanners Apart from saving space and maintenance costs , cryogen gas recycling devices replace liquid nitrogen core , as there is no need to maintain magnet at absolute zero temperatures . Parallel imaging methods for encoding the MRI signals , replace the phased array coil technology which reduces the time required for obtaining MR image and also reduces the number of RF pulses , for image formation

Most often purchasers of MRI scanners face difficulty in deciding to buy one . This is because , the MRI is very expensive and is still considered an evolving technology . Although the initial cost is too high , the number of MRI scanners used in the US is growing . Though the features and the possibilities with the MRI is growing significantly , its cost is relatively being lowered (Clarke , 2004 . This trend would ensure that in the Magnetic Resonance Imaging 4

next five to eight years , the cost of the MRI wouldn 't be expensive given the logic and anticipated cost reductions in gradient technologies and computers

The uses of MRI can be endlessly stated , which rests on the backdrop of the fact that even the smallest of the structures in the body can be seen with unprecedented clarity (WRA . Therefore it is no wonder that the majority of MRI scans is related to spinal cord , nerves , brain breasts , abdomen and pelvic organs . MRI poses no perceived risk in children and adults , as they don 't use x-rays

REFERENCES

Radiological Society of North America (2007 ) MRI of the body (Chest Abdomen , Pelvis . [Electronic Version] Downloaded on 25th March 2008 from

HYPERLINK "http /www .radiologyinfo .org /en /info .cfm ?pg bodymr bhcp 1 http /www .radiologyinfo .org /en /info .cfm ?pg bodymr bhcp 1

Geoffrey Clarke (July , 2004 ) State of the Art MRI : A Technology Update Imaging Economies [Electronic Version] Downloaded on 25th March 2008 from

HYPERLINK "http /www .imagingeconomics .com /issues /articles /2004-07_05 .asp http /www .imagingeconomics .com /issues /articles /2004-07_05 .asp

Nagasaki University School of Medicine (2002 ) Introduction to MRI history . [Electronic Version] Downloaded on 25th March 2008 from

HYPERLINK "http /www .med .nagasaki-u .ac .jp /radiolgy /MRI 20of 20the 20FOOT /MRI-CDNU H /nf-history .html http /www .med .nagasaki-u .ac .jp /radiolgy /MRI 20of 20the 20FOOT /MRI-CDNUH /nf-history .html

Hornak J .P (2007 ) The basics of MRI [Electronic Version] Downloaded on 25th March 2008 from HYPERLINK "http /www .cis .rit .edu /htbooks /mri /inside .htm http /www .cis .rit .edu /htbooks /mri /inside .htm

Washington Radiology Associates MRI - Frequently asked questions [Electronic Version] Downloaded on 25th March 2008 from HYPERLINK "http /www .washingtonradiology .com /exams /mri /patfaq .html http /www .washingtonradiology .com /exams /mri /patfaq .html ...